WO2001068001A1

WO2001068001A1 - Endoprosthesis for a knee-joint

Info

Publication number: WO2001068001A1
Application number: PCT/DE2001/000995
Authority: WO
Inventors: Günter Rehder
Original assignee: Saint-Paul, Bernd
Priority date: 2000-03-14
Filing date: 2001-03-14
Publication date: 2001-09-20
Also published as: EP1411870A1; DE10012060A1; DE10012060C2

Abstract

The invention relates to an endoprosthesis for a knee-joint. The inventive endoprosthesis comprises a femur and a tibia component which can be anchored in the respective bone and a meniscus component which has bearing shells, is dorsally/ventrally arranged between the femur component and the tibia component, on an even tibia plateau and in a guidance in a displaceable manner and acts as the artificial meniscus. Said bearing shells engage with condyle running surfaces of the femur component. The meniscus component (3) is provided with a bridge (7) on the ventral side thereof and between the bearing shells (5). Said bridge (7) engages between the condyle running surfaces (6) on the femur component (2). A dowel pin (11) is mounted on the tibia plateau (8) of the tibia component (4). Said pin protrudes into a lower guiding groove (12) in the meniscus component (3) under the bridge (7). A stopper (9) is mounted on the ventral end of the tibia plateau (8). The stopper (9) engages with a recess (10) that is inserted into the lower, ventral edge of the meniscus component (3) and glides therein. Bearing components (13) for the meniscus component (3) are arranged above the tibia plateau (8). Said bearing components (13) are designed in such a way that said components (13) can be displaced in bearing pockets (14) in the tibia plateau and are spherical on the upper side thereof.

Description

Endoprosthesis for a knee joint Description:

The present invention relates to an endoprosthesis for a knee joint, with a femur part and a tibia part that can be anchored in the respective bones. and a meniscus part with bearing shells which is displaceably mounted dorsally / ventrally in a guide between the Fermur part and the tibia part on a flat tibial plateau as a meniscus part with bearing shells which are in engagement with the condylar running surfaces of the femur part. Such an endoprosthesis is known from EP 0 529 408 AI.

The aim of these and other prostheses is that a knee joint can largely carry out the previous natural sequence of movements after implantation of a knee joint prosthesis. A simple hinge movement between the femur part and the tibia part does not do justice to this special physiological kinematics and statics. which resulted in not inconsiderable difficulties in terms of functional reliability, durability and resilience in the known prostheses. According to these findings, the human knee has five degrees of freedom of movement. The sequence of movements in a natural knee joint is relatively complicated due to a superimposed rolling and sliding movement when bending or stretching a leg. For example, a knee joint is primarily a hinge joint that is fully locked in the stretched state, but thanks to the design as a double joint when the leg is bent, it also allows the lower leg to rotate about its longitudinal axis. It is essentially formed by only two bones, namely the two "articulated rollers" (condyles) and the plateau-like articular surface of the tibia (tibia), while the fibula is not directly involved in the formation of the joint and only serves as an approach for a side ligament Equalization of the articular surfaces serve two crescent-shaped wedge-shaped intervertebral discs (inner and outer meniscus) which not only absorb shocks and pressure when walking, running and jumping, but also ensure due to their relative mobility to the femur and the tibia that it does not cause bending of the knee joint The known knee prostheses have so far not been able to replicate the five degrees of freedom of movement of the human knee.

Endoprostheses for a partial or complete replacement of a knee joint are also known as sled or unicondilar prostheses or as bicondylar prostheses in a wide variety of configurations, the selection of the prostheses to be implanted being determined by different aspects. So the choice of the type of prosthesis depends e.g. B. from it. whether the ligamentous apparatus of the patient's knee is still functioning or has been completely destroyed. The invention here deals specifically with endoprostheses for knee joints in which the ligamentous apparatus is still present or is still largely available. so that a positive connection between the femur and tibia part. which connects the two parts, for example by means of a flexible joint, can be dispensed with.

The invention is therefore based on the object of developing the endoprosthesis of the type mentioned in such a way that the physiological knee function movement and loading and the knee joint can largely perform the previous natural movement sequence after implantation of a prosthetic knee joint. The forces should be transferable to the largest possible area and local load peaks, especially as a result of line and point contact, should be avoided. The prosthesis should have small dimensions and the physiological kinematics and statics should also be ensured even if the ligament function is only partially intact. Furthermore, good tribological properties with regard to the parts that can be moved relative to one another and a high static strength of the force-transmitting parts should be ensured. Frictional forces between the individual components that can be moved relative to one another should be minimized, in particular the static friction at the start of a movement.

To achieve this object, the present invention proposes the features which are shown in the characterizing part of patent claim 1. Further advantageous features for fulfilling the task are set out in the characterizing features of the subclaims.

The endoprosthesis proposed by the invention ensures an optimal implementation of the physiological kinematics and statics of the human knee with reliable and compact construction, with local stress peaks being reliably avoided. Due to the special design of the meniscus part, the translational and rotational five degrees of freedom of movement of the human knee are guaranteed.

Details of the invention are explained in more detail below and with reference to FIGS. 1 to 6. Show it:

1 is a representation of the five degrees of freedom of movement of the human knee joint,

2 shows a longitudinal section of the endoprosthesis for a knee joint in the extended position,

3 shows the endoprosthesis according to FIG. 2 in a dorsal view,

4 shows the exploded view of the endoprosthesis according to FIG. 2,

5 shows an exploded view of the endoprosthesis according to FIG.

6a to 6d show a section approximately along AB in FIGS. 2 and 3 with different rotations about the imaginary vertical axis through the knee joint, elements outside the cutting plane also being adopted for better illustration of the function.

7a to 7c a prosthesis with a modified guide pin, 7a an exploded view, 7b a view similar to FIGS. 6 and 7c a section in the assembled state. 1 shows the five degrees of freedom of the movements of the human knee to illustrate its function. The X axis determines the sagittal, the Y axis the vertical and the Z axis the transverse direction. The five degrees of freedom of the knee are:

1.) Rotation around the Z axis (Rz) with diffraction and extension

2.) Rotation around the Y axis (Ry) with axial rotation

3.) Rotation around the X-axis (Rx) when tilted during abduction and adduction

4.) Translation in the X axis with sagittal displacement of the tibia and femur

5.) Translation in the Z axis with transverse displacement of the tibia and femur.

The bicondular new endoprosthesis 1 shown in FIGS. 2 to 6 is a replacement for the sliding surfaces of the human knee with the ligament apparatus still or largely functioning. It essentially consists of the femoral part 2, the meniscus part 3 and the tibia part 4. The rotation and translation of the knee being controlled and limited by the ligamentous apparatus when the ligamentous apparatus exists. The femur part 2 is anchored with a pin 19 in the medullary canal of the femur and the tibia part 4 by a shaft 20 in the medullary canal of the tibia, two additional rotation locks 21 being provided on the tibia part 4 in addition to the shaft 20 for further anchoring in the bone of the tibia. Between the femur part 2 and the tibia part 4, the artificial meniscus part 3 is arranged, on the top of which two adjacent bearing shells 5 are introduced, which are in engagement with the two correspondingly adjacent and circularly shaped condyle treads 6 on the femur part 2, so that the treads 6 in the Bearing shells 5 slide and the femoral part 2 can rotate therein about the axis Z as Rz.

On its ventral side between the bearing shells 5, the meniscus part 3 has a bridge 7, which stands above it and engages between the condyle running surfaces 6 on the femur part 2 and limits the transverse movement of the femur part 2, that is to say the translation Tz in the Z axis. For this purpose, a guide pin 11 is inserted on the tibia plateau 8 of the tibia part 4, which protrudes into a lower, elongated ventral / dorsally formed guide groove 12 in the meniscus part 3 under the bridge 7 and limits its translation Tx to the length of this guide groove 12. To further limit the translation Tx, an upstanding collar is attached as a stop 9 on the ventral end of the tibial plateau 8, which engages in a crescent-shaped recess or recess 10, which is introduced into the lower ventral edge of the meniscus part 3 and in which the stop 9 slides laterally back and forth during rotation Ry about the y axis and the guide pin 11 resting against the ventral end of the recess 12 (see FIGS. 6a-c).

In order to enable the flexion angle to be compensated for during the rotation Rz about the Z axis and the displacement of the tibia part 4 against the femoral part 2 in the sagittal direction, that is to say the translation Tx, a medial and a lateral bearing part 13 for the meniscus part are located above the tibial plateau 8 3 arranged. For this purpose, the bearing parts 13 are each displaceably arranged in a further, circumferentially closed storage pocket 14 in the tibial plateau 8 by means of the control rollers 16 running horizontally on their inner side surfaces and protruding top is spherical. The curved heads 1 5 engage in a form-fitting manner in correspondingly dome-shaped bearing pockets 1 7 on the underside of the meniscus part 3 and thus enable its movement on the tibial plateau 8 within the limit specified by the dimensions of the bearing pocket 1 4, these dimensions of course being larger than the diameter the control rollers 16 are. The control rollers 16 running in the bearing pocket 14 also limit the rotation Ry about the Y axis.

The meniscus part 3 is bevelled on its underside at its dorsal end. the bevel 18 is preferably at an angle of 10 ° to the tibial plateau 8. This beveling on the dorsal side facing the tibia and the spherical configuration of the bearing parts 13 which engage in the bearing pockets 1 7 result in the meniscus part 3 tipping over the bevel at the maximum deflection, that is to say the rotation Rz about the Z axis 18 reached the bottom of the meniscus part 3. This tilting compensates for the change in the angle to the circular condyle running surfaces 6.

6a-d show a rotation of the prosthesis from the extended position into the flexed position with simultaneous rotation about the Y-axis and its limitation by the stop of the control rollers 16 as well as the guide groove 12 and the stop 9 on the ventral recess 10. However, the figures do not exactly follow the course of the cut in order to be able to depict the interlocking parts more clearly. 6a shows a schematic view of the meniscus part 3, the extended position of the prosthesis with ventral rotation and a ventral stop of the control rollers 16 taking place here, and FIG. 6b shows the maximum deflection without a rotation stop of the control rollers 16 in the same view. FIG. 6c shows the position with a maximum diffraction with simultaneous medial rotation about Ry and FIG. 6d shows a corresponding bottom view at a flexion angle of 45 degrees with lateral rotation deflection.

The design of the condylar running surfaces 6, the meniscus part 3 and that of the various bearings can differ depending on the material used. The individual configurations can be specified depending on the materials used. The design of the individual components of the prosthesis make it possible for the articulating parts femur- 2nd tibia- 4th meniscus- 3, bearing part 13 and control rollers 16 made of metal optionally coated or uncoated, made of ceramic, optionally coated or uncoated, and the meniscus part 3 the prosthesis made of metal or ceramic can either be coated or uncoated made of plastic.

FIGS. 7a-c show an embodiment of the endoprosthesis which is suitable for use in the case of insufficient ligament tensioning of the remaining ligament apparatus. In such cases, the meniscus may dislocate from the tibial plateau. Therefore, in the embodiment according to FIGS. 7a-c, the meniscus part 3 is positively held or secured against lifting off from the tibia part 4 while maintaining the mobility. This takes place in that the former guide pin 11 is replaced by a guide pin 22 screwed into the tibial plateau 8, which has a head 23 of larger diameter with an internal hexagon. The bolt 22 slides, similar to the guide pin 1 1 in the Guide groove 12 in Figures 2 to 6, ventral / dorsal in an elongated hole-like guide groove 24 penetrating the bridge 7 with an upper extension 25, wherein its head 23 comes to rest in this extension 25 and can slide in it. The upper extension 25 is as wide as the head diameter and as long as the guide groove 24 plus two protrusions of the head 23 compared to the diameter of the bolt 22. The play of this connection can be selected as required. This positive guidance or positive connection reliably prevents dislocation while maintaining the mobility of the meniscus part 3 sliding on the tibial plateau 8 and thus considerably improves the stability and wearing properties of the prosthesis.

LIST OF REFERENCE NUMBERS

1 endoprosthesis

2 femoral part

meniscus part

4 tibia part

5 cups

6 condylar treads

7 bridge

8 Tibial Plateau

9 stop

1 0 recess, recess

1 1 guide pin

12 guide groove

1 3 bearing parts

14 storage pockets

1 5 ball heads

16 steering rollers

1 7 storage pockets

1 8 bevel

19 cones

20 shaft

21 rotation lock

22 guide bolts

23 head

24 guide groove

25 extension

Claims

claims:

1 . Endoprosthesis for a knee joint, with a femoral part and a tibia part that can be anchored in the respective bones, as well as a meniscus part with bearing shells that is slidably mounted dorsally / ventrally in a guide between the fermural part and the tibia part on a flat tibia plateau are involved, characterized by the following features:

a) the meniscus part (3) has on its ventral side between the bearing shells (5) a bridge (7) which rises above these and engages between the condyle running surfaces (6) on the femur part (2),

b) on the tibial plateau (8) of the tibia part (4) a guide pin (1 1) is inserted, which protrudes into a lower guide groove (12) in the meniscus part (3) under the bridge (7).

2. Endoprosthesis according to claim 1, characterized by the further features:

c) on the ventral end of the tibial plateau (8) there is a stop (9) which engages in a recess (10) introduced into the lower ventral edge of the meniscus part (3) and slides back and forth therein.

3. Endoprosthesis according to claim 1 or 2, characterized by the further features:

d) Above the tibial plateau (8) are bearing parts (13) for the meniscus part (3), which are each displaceable in a bearing pocket (14) in the tibial plateau (8) by means of control rollers (16) and on them, via the tibial plateau (8 ) protruding top are spherical.

4. Endoprosthesis according to claim 3, characterized by the further features:

e) the curved heads (15) of the bearing parts (13) positively engage in correspondingly dome-shaped bearing pockets (17) on the underside of the meniscus part (3).

5. Endoprosthesis according to one of the preceding claims, characterized by the further features:

f) the meniscus part (3) is provided on its underside at its dorsal end with a bevel (1 8).

6. Endoprosthesis according to claim 5, characterized by the further features:

g) the bevel (1 8) is at an angle of approximately 10 ° to the tibial plateau (8.

7. Endoprosthesis according to one of the preceding claims, characterized by the further features:

h) the meniscus part (3) is held against the tibia part (4) in a positive manner against lifting while maintaining the mobility.

8. Endoprosthesis according to claim 7, characterized by the further features:

i) a guide bolt (22) is screwed into the tibial plateau (8), which has a head (23) of larger diameter and in a guide groove (24) made in the bridge (7) with an upper extension (25) for receiving the head (23 ) slides.

9. Endoprosthesis according to one of the preceding claims, characterized by the further features:

j) the tibia part (4) is anchored by a shaft (20) in the medullary cavity of the tibia, two additional rotation locks (21) being provided on the tibia part (4) in addition to the shaft (20) for further anchoring in the bone of the tibia.

10. Endoprosthesis according to one of the preceding claims, characterized by the further features:

k) the meniscus part (3) consists of plastic

1 1. Endoprosthesis according to one of the preceding claims, characterized by the further features:

1) the articulating parts, femur (2), tibia (4), meniscus (3), bearing parts (1 3) consist of uncoated or coated ceramic.

12. Endoprosthesis according to one of claims 1 to 10, characterized by the further characteristics:

m) the articulating parts, femur (2), tibia (4), meniscus part (3) consist of uncoated or coated metal.